Population connected to at least secondary wastewater treatment

This indicator measures the percentage of the population connected to wastewater treatment systems with at least secondary treatment. Thereby, wastewater from urban or other sources is treated by a process generally involving biological treatment with a secondary settlement or other process that removes organic material and reduces its biochemical oxygen demand (BOD) by at least 70 % and chemical oxygen demand (COD) by at least 75 %. Data presented in this section stem from the Water Statistics of the European Statistical System (ESS).